Share

The considerable recent drop in HIV diagnoses among men who have sex with men attending five London sexual health clinics is likely the result of an increasing proportion of HIV-positive MSM at the clinics going on treatment for the virus, aidsmap reports. A sudden burst in the number of HIV-negative MSM attending these clinics who have started accessing Truvada (tenofovir disoproxil fumarate/emtricitabine) as pre-exposure prophylaxis (PrEP) likely contributed to the drop in diagnoses as well.

Increasing research has suggested that achieving an undetectable viral load with antiretroviral (ARV) treatment likely all but eliminates the risk of passing HIV on to others; the risk may in fact be zero. This benefit of ARVs is known as treatment as prevention, or TasP.

Presenting their findings at the British HIV Association (BHIVA) conference in Liverpool, researchers looked at data on new HIV diagnoses across England through the third quarter of 2016.

Looking at the five London clinics in question, researchers found that during 2015, the clinics each saw more than 200 new HIV diagnoses per quarter, compared with 100 to 150 diagnoses per quarter in 2016. This drop occurred as HIV testing rates rose, so reduced testing is not driving down the rate of diagnoses.

In recent years, the five clinics have all reduced the average time between HIV diagnosis and the start of ARV treatment, from a median 450 days in 2011 to 180 days in 2013 and 100 days in 2015. Meanwhile, the estimated number of MSM attending these clinics who have a viral load above 200, including those with diagnosed as well as undiagnosed HIV, fell from about 4,000 in 2014 to 1,700 in 2015.

Researchers have developed a new measure known as the transmissibility ratio to help gauge how TasP may affect transmission rates. The figure is calculated by dividing the estimated number of HIV-positive men at a clinic who have a detectable viral load by the number of HIV-negative men considered at high risk of contracting the virus.

At these five clinics, there were 1,752 MSM with detectable HIV and 3,596 high-risk men, yielding a transmissibility ratio of 0.5. Any ratio below 1 characterizes a low overall risk of transmission. Other London clinics and those outside the city had a ratio of 1.7 in both cases.

At one of the clinics that saw a steep drop in HIV diagnoses, known as 56 Dean Street, about 700 MSM reported using PrEP between February 2016 and February 2017. PrEP is not widely available in the United Kingdom yet, so many MSM have been obtaining it through the internet. Several London clinics have been working to support those accessing the HIV prevention tool in this unorthodox way.